Reciprocal space mapping of implanted AIIIBV semiconductor compounds

The reciprocal space maps around the 400 reciprocal space point were collected for a number of different implantations in GaAs and Al_xGa_1−xAs including high dose implantations (∼10¹⁶ ions/cm²) with 1.5 MeV Se⁺ and As⁺ ions. We also studied the effect of high pressure annealing in GaAs implanted with 170 keV protons. The maps were recorded from an area of 50×100 μm² with a very good resolution of details. The maps usually revealed the same sequence of interference maxima as the double crystal rocking curves recorded with a widely open detector slit. This series of maxima was also well reproduced in numerically calculated theoretical rocking curves. The maxima were usually located exactly along the central θ/2θ scan. In one case we observed a deviation of the interference maxima from the θ/2θ direction, connected with lateral strain changes and consequent tilt deformation of the lattice. The maps for as implanted layers did not reveal significant diffuse scattering. A significant increase of diffuse scattering was present in proton implanted GaAs after thermal annealing performed at 450 °C under 11 kbar of argon pressure for a sample implanted with 170 keV protons with a dose 2·10¹⁶ cm⁻².     

2 MeV ion irradiation effects on AlGaN/GaN HFET devices

AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with 2 MeV protons, carbon, oxygen, iron and krypton ions with fluences ranging from 1 × 10⁹ cm^?2 to 1 × 10¹³ cm^?2. DC, pulsed I–V characteristics, loadpull and S-parameters of the AlGaN HFET devices were measured before and after irradiation. In parallel, a thick GaN reference layer was also irradiated with the same ions and was characterized by X-ray diffraction, photoluminescence, Hall measurements before and after irradiation. Small changes in the device performance were observed after irradiation with carbon and oxygen at a fluence of 5 × 10¹⁰ cm^?2. Remarkable changes in device characteristics were seen at a fluence of 1 × 10¹² cm^?2 for carbon, oxygen, iron and krypton irradiation. Similarly, remarkable changes were also observed in the GaN layer for irradiations with fluence of 1 × 10¹² cm^?2. The results found on devices and on the GaN layer were compared and correlated.     

Control strategy of electrolyzer in a wind-hydrogen system considering the constraints of switching times

In order to improve the operational performance of alkaline electrolyzers powered by wind power, the influences of the fluctuating wind power on alkaline electrolyzers must be taken in accounts. In pursuing this goal, the influences of fluctuating wind power on both the hydrogen production and the self-safety of alkaline electrolyzer is discussed firstly. And a wind-hydrogen integrated energy system (WHIES) integrated supercapacitor is designed to smooth the fluctuation of wind power. In which, the fluctuation of wind power is divided into two kinds, instantaneous fluctuation and wide power fluctuation, the former is absorbed by supercapacitors, the latter is overcomed by adopting a modular adaptive control strategy to optimize the operation mode of alkaline electrolyzer. A simulation has been developed for a specific wind farm located in Northeast China. The simulation results show that under the condition of fluctuating wind power, the WHIES with the proposed control strategy can reduce the switching times of electrolyzers by 93.5% and increase hydrogen production by more than 44.18% when compared with other control strategies.     

Mortars,pigments and saline efflorescence from Canarian pre-Hispanic constructions (Galdar,Grand Canary Island)

Construction elements of the ancient caves of Galdar (Grand Canary Island) give details of the life of isolated, prehistoric island inhabitants (pre-Hispanic Canarians) and their adaptation to a dry volcanic environment. Mineralogical study samples of host rocks, mortars, pigments and saline efflorescence by X-ray diffraction and electron microscopy allow us to explain their local origin, development grade and environmental factors of degradation. Regional tephra pyroclasts are composed of volcanic glass and euhedral phenocrysts of pyroxene and olivine, with traces of biotite and apatite. Cream mortars are calcite, apatite and feldspars; white are calcite-halloysite; grey calcite with iron oxides and the argillaceous plasters are mixtures of illite, montmorillonite, kaolinite and chlorites. Red-ochre pigments are oxo-hydroxides of iron-manganese, whites are halloysite, and blacks are silica mixtures of Mg, Fe, Mn, Ti, K and Ca, collected from the host-tephra (pyroxene, biotite, spinel, pyrolusite and iron oxides). The main saline efflorescences consist of thenardite and trona (sodium salts) from the watering of modern crops fields and gypsum from the restoration works (concrete) of the archaeological park in 1997. The ancient population used numerous combinations of local minerals to prepare beautiful paintings, which were protected underground below pyroclastic deposits until modern times, when they were dug out and flooded with saline waters, which produced serious alterations. Additional care must be taken to protect these prehistoric constructions.     

Size effects in the fatigue behavior of thin Ag films

Thin film dimensions and microstructure affect the microscopic processes responsible for fatigue. This work focuses on the characterization of such mechanisms and the resulting fatigue behavior. The fatigue behavior of 0.2–1.5 μm thick, Ag films on SiO₂ was investigated. The films were tested using cantilever microbeam deflection with respect to the influence of loading conditions. Extrusions similar to those observed in bulk material were found at the Ag film surfaces after cyclic loading. Voids observed beneath the extrusions, close to the film-substrate interface, contributed significantly to fatigue failure. Fatigue damage was observed to occur predominantly in (100)-oriented grains. Thinner films were more fatigue resistant and contained fewer, smaller extrusions than thicker films.     

Towards an improved readability on mobile devices: evaluating adaptive rapid serial visual presentation

Can readability on small screens be improved by using adaptive Rapid Serial Visual Presentation (RSVP) that adapts the presentation speed to the characteristics of the text instead of keeping it fixed? In this paper we introduce Adaptive RSVP, describe the design of a prototype on a mobile device, and report findings from a usability evaluation where the ability to read long and short texts was assessed. In a latin-square balanced repeated-measurement experiment, employing 16 subjects, two variants of Adaptive RSVP were benchmarked against Fixed RSVP and traditional text presentation. For short texts, all RSVP formats increased reading speed by 33% with no significant differences in comprehension or task load. For long texts, no differences were found in reading speed or comprehension, but all RSVP formats increased task load significantly. Nevertheless, Adaptive RSVP decreased task load ratings for most factors compared to Fixed RSVP. Causes, implications, and effects of these findings are discussed.     

An approach to the estimation of the value of agricultural residues used as biofuels

A simple demand side approach for estimating the monetary value of agricultural residues used as biofuels is proposed. Some of the important issues involved in the use of biomass feedstocks in coal-fired boilers are briefly discussed along with their implications for the maximum acceptable price estimates for the agricultural residues. Results of some typical calculations are analysed along with the estimates obtained on the basis of a supply side approach (based on production cost) developed earlier. The prevailing market prices of some agricultural residues used as feedstocks for briquetting are also indicated. The results obtained can be used as preliminary indicators for identifying niche areas for immediate/short-term utilization of agriculture residues in boilers for process heating and power generation.